1. Field of the Invention
The present invention relates to a ceramic electronic component.
2. Description of the Related Art
Ceramic capacitors are typical examples of ceramic electronic components, wherein a number of internal electrode layers are embedded in a ceramic body composed of, for example, BaTiO3. The internal electrode layers are opposed to each other with an ultrathin ceramic layer interposed therebetween. The ceramic body includes outer layers at both sides in the thickness direction. The outer layers are sufficiently thicker than the ceramic layer interposed between the internal electrode layers. In addition, terminal electrodes that are continuous to the internal electrode layers are attached to both side faces in the length direction. The ceramic body is exposed externally at all the faces other than the side faces with the terminal electrodes attached thereto.
In ceramic electronic components of this type, as described above, since the surface of the ceramic body serves as an outer surface except the side faces with the terminal electrodes attached thereto, the ceramic body itself is required to have such a physical property as to resist cracking or breaking when subjected to an external impact.
However, ceramic electronic components of this type are manufactured such that a green chip (before firing) embedded with a number of internal electrode layers is fired and after firing, the terminal electrodes are attached thereto. At this firing step, there is a problem that mechanical strength is decreased due to insufficient firing of the outermost ceramic layer, easily causing cracking or breaking in the ceramic body.
As means for solving the above problem, Japanese Unexamined Patent Application Publication No. 2001-44069 discloses a technology that after formation of the external electrode (terminal electrode), the entire outer surface is coated with an oxide glass to form a glass coating layer, and then the glass coating layer is polished outside the electrode covering portion of the terminal electrode to exposed the surface of the terminal electrode.
In the above prior art, however, there is required a cumbersome, complicated process that after formation of the terminal electrode, a glass coating layer is formed by coating with an oxide glass and then the surface of the terminal electrode is exposed by polishing the glass coating layer outside the electrode covering portion of the terminal electrode. In addition, since the glass coating layer serves as a protective layer, the occurrence of cracking cannot be perfectly prevented because of the nature of glass.
In ceramic electronic components of this type, moreover, since the surface of the ceramic body serves as an outer surface except the side faces with the terminal electrodes attached thereto, the ceramic body has to be provided with not only sufficient moisture resistance but also the function of preventing a surface leakage current that will flow between the terminal electrodes. The surface leakage current occurs, for example, when an impurity adheres to the surface of the ceramic body between the terminal electrodes, and therefore, in order to prevent this problem, the ceramic body has to be provided with such a surface property that an impurity hardly adheres thereto. Particularly in recent ceramic electronic components, e.g., a ceramic capacitor, since the distance between the terminal electrodes is extremely shortened due to the rapid progress of miniaturization and slimming down, the surface leakage current easily occurs when an impurity adheres to the ceramic body exposed between the terminal electrodes.
There has been known no prior art that is aware of and discloses means for solving the above problem, including the above-identified Patent Document.